Hugo Sol - Academia.edu (original) (raw)
Papers by Hugo Sol
Proceedings of the International Conference on Advanced Technology in Experimental Mechanics, Sep 1, 2007
no ISBNstatus: publishe
The basic principle of inverse methods for the identification of material model parameters is to ... more The basic principle of inverse methods for the identification of material model parameters is to compare measured observations on a test specimen in a given test setup with virtual observations computed with a numerical model of the test specimen. The unknown parameters in the numerical model are updated until the computed observations match the measurements. Many inverse methods have already been proposed for the identification of uniform material properties in beamlike or plate like specimens based on a limited amount of observations. However, if the material properties in the specimens vary from point to point, more measured observation information is necessary. This paper presents an inverse method that can identify the local bending stiffness distribution in test beams based on the observation of the curvatures of vibration mode shapes. The test beams are freely suspended and the mode shapes are activated by acoustical excitation. The curvatures of the mode shapes are measured ...
EPJ Web of Conferences, 2010
Applied Composite Materials, 1997
Experimental Mechanics, 2007
Inverse methods offer a powerful tool for the identification of the elasto-plastic material param... more Inverse methods offer a powerful tool for the identification of the elasto-plastic material parameters. One of the advantages with respect to classical material testing is the fact that those inverse methods are able to deal with heterogeneous deformation fields. The basic principle of the inverse method that is presented in this paper, is the comparison between experimentally measured strain fields and those computed by the finite element (FE) method. The unknown material parameters in the FE model are iteratively tuned so as to match the experimentally measured and the numerically computed strain fields as closely as possible. This paper describes the application of an inverse method for the identification of the hardening behavior and the S. Cooreman (B, SEM member) • D. Debruyne
Conference Proceedings of the Society for Experimental Mechanics Series, 2013
Shearography is an interferometric method that produces full-field displacement gradients of the ... more Shearography is an interferometric method that produces full-field displacement gradients of the inspected surface. In high-technology industry it is often used qualitatively to detect material defects, but quantitative applications are still rare. The reasons for that are the complicated calibration procedure as well as the denoising, unwrapping, the local sensitivity vector estimation and the local shearing angle estimation needed to get quantitative gradient-maps. To validate the technique and its calibration, results obtained from shearography are compared to results obtained from scanning laser vibrometry. Beams are acoustically excited to vibrate at their first resonant frequency and the mode shape is recorded using both shearography and scanning laser vibrometry. Outputs are compared and their properties discussed. Separate inverse method algorithms are developed to process the data for each method. They use the recorded mode shape information to identify the beam’s local stiffness distribution. The beam’s stiffness is also estimated analytically from the local geometry. The local stiffness distributions computed using these methods are compared and the results discussed.
Increasing oil prices have intensified the trend to use composite materials in so-call primary co... more Increasing oil prices have intensified the trend to use composite materials in so-call primary components of cars and in aerospace applications. As a consequence, the fatigus behaviour of composites has became an important issue. This paper describeds accelerated fatigue tests on composite material beam specimens clamped in their middle part and fixed on an electromechanic shaker. Many loading cycles can be imposed on a specimen in a controlled way by inducing resonance vibrations. The bending mode shape that is associated to the fundamental resonance frequency causes a stress state in the specimen that is maximal at the clamping pont in the middle and zero at both free ends. The stress state and hence the fatigue behavior varies from point to point. By interrupting the fatigue test at well-chosen moments in time and measuring the amplitude distribution of the vibration mode, it is possible to calculate the evolutio of the beam stiffness as a function of the number of applied loadin...
The mixed numerical/experimental techniques (MNET), in which the numerical results are correlated... more The mixed numerical/experimental techniques (MNET), in which the numerical results are correlated with experimental data in an iterative fashion, has been developing for more than two decades. An overview of the various estimation algorithms in the MNET is given. Emphasis is placed on the different philosophies which may lead to a deterministic optimisation procedure, or a statistical estimator, or a combination of the two. Formulations, limitations and internal relations of the algorithms are also presented. All the discussions are oriented to the researchers and engineers who are interested in the design optimisation, parameter identification and finite element model updating.
The basic principle of an inverse modeling procedure as it is used for parameter identification, ... more The basic principle of an inverse modeling procedure as it is used for parameter identification, is the generation of a complex and heterogeneous deformation field that contains as much information as possible about the parameters to be identified. One way of obtaining such a non-homogeneous deformation is by making the geometry of the specimen less regular. Another possibility is to make the loading conditions more complex. In this paper both options are actually combined by using a biaxial tensile test on a cruciform specimen in order to identify the parameters of a Swift isotropic hardening law. The yield criterion is modeled by the isotropic Von Mises criterion. The optimization technique used is a constrained gradient based Newton-type routine, which means that in every iteration step, a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be optimized. The functional to be minimized is a least-squares expression of the d...
Incremental forming is a generalized term of metal forming processes where tools of common shapes... more Incremental forming is a generalized term of metal forming processes where tools of common shapes are used to form a small portion of the work piece consecutively next to another resulting in a desired shape. Where die-sets are exclusively designed for particular shapes, one can produce complex forms using a combination of a simple tool and a simplified die. [1,2,5,6] Although ordinary press forming requires less time and is more cost effective in large series production than incremental forming, this new process offers interesting perspectives in small volume production and rapid prototyping [1,2,5,6]
The accuracy of a Finite Element Simulation for plastic deformation strongly depends on the chose... more The accuracy of a Finite Element Simulation for plastic deformation strongly depends on the chosen constitutive laws and the value of the material parameters within these laws. The identification of those mechanical parameters can be done based on homogeneous stress and strain fields such as those obtained in uniaxial tensile tests and simple shear tests performed in different plane material directions. Another way to identify plastic material parameters is by inverse modeling of an experiment exhibiting a heterogeneous stress and strain field. Experimental forces and strains are in this case compared to the simulated ones and it is tried to reduce the difference in a least-squares sense by optimizing the model parameters. The optimization technique used is this case is gradient based, which means that at every iteration a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be identified. The basic principle of the inverse mo...
The quest for more sophisticated methods imparts a significant challenge in the field of nondestr... more The quest for more sophisticated methods imparts a significant challenge in the field of nondestructive testing (NDT) and material characterization. In this paper, we present and discuss experimental polar scans of typical carbon fibre reinforced composite materials recorded with shock wave transducers at frequencies ranging from 1 to 5 MHz. Besides the well-known measurements performed in transmission (T) and double through transmission (2T), we here introduce new investigations based on polar scans of both the backscattered and the double-double through transmission (4T) signals. Amplitude as well as the time of flight diffraction (TOFD) values of the peak amplitude are recorded as a function of the scanned solid angle. One the one hand, it is shown that sharper and more detailed polar scans, especially in TOFD recording, are obtained with the 4T method, which is advantageous for stable polar contour extraction and consequently for inferring the elasticity constants C-ij of the ma...
Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained partic... more Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained particular interest in rapid prototyping and small volume production. The study of the underlying forming mechanisms is supported by new developments in finite element simulations and experimental full field strain measurements. This article aims to describe the possibilities and difficulties encountered during validation of finite element predictions of the incremental forming process. The drawing of a straight line into a metal plate was selected as a first test case for this kind of validation. Results of both finite element simulation and experimental work will be discussed.
Since there is a large demand for biaxial experimental data to evaluate existing failure criteria... more Since there is a large demand for biaxial experimental data to evaluate existing failure criteria, a plane biaxial test device was developed at the Vrije Universiteit Brussel. In-plane loads are applied to a cruciform specimen in order to create a known biaxial stress state in the centre of the specimen. The experiments accomplished in the past and present at the author’s institution have as main intention the biaxial strength and stiffness characterization of fibre-reinforced composite materials. The results from quasi-static tests have been analysed thoroughly in the past [1,2]. The study of the biaxial fatigue behaviour is however in a less advanced stage.
Proceedings of the International Conference on Advanced Technology in Experimental Mechanics, Sep 1, 2007
no ISBNstatus: publishe
The basic principle of inverse methods for the identification of material model parameters is to ... more The basic principle of inverse methods for the identification of material model parameters is to compare measured observations on a test specimen in a given test setup with virtual observations computed with a numerical model of the test specimen. The unknown parameters in the numerical model are updated until the computed observations match the measurements. Many inverse methods have already been proposed for the identification of uniform material properties in beamlike or plate like specimens based on a limited amount of observations. However, if the material properties in the specimens vary from point to point, more measured observation information is necessary. This paper presents an inverse method that can identify the local bending stiffness distribution in test beams based on the observation of the curvatures of vibration mode shapes. The test beams are freely suspended and the mode shapes are activated by acoustical excitation. The curvatures of the mode shapes are measured ...
EPJ Web of Conferences, 2010
Applied Composite Materials, 1997
Experimental Mechanics, 2007
Inverse methods offer a powerful tool for the identification of the elasto-plastic material param... more Inverse methods offer a powerful tool for the identification of the elasto-plastic material parameters. One of the advantages with respect to classical material testing is the fact that those inverse methods are able to deal with heterogeneous deformation fields. The basic principle of the inverse method that is presented in this paper, is the comparison between experimentally measured strain fields and those computed by the finite element (FE) method. The unknown material parameters in the FE model are iteratively tuned so as to match the experimentally measured and the numerically computed strain fields as closely as possible. This paper describes the application of an inverse method for the identification of the hardening behavior and the S. Cooreman (B, SEM member) • D. Debruyne
Conference Proceedings of the Society for Experimental Mechanics Series, 2013
Shearography is an interferometric method that produces full-field displacement gradients of the ... more Shearography is an interferometric method that produces full-field displacement gradients of the inspected surface. In high-technology industry it is often used qualitatively to detect material defects, but quantitative applications are still rare. The reasons for that are the complicated calibration procedure as well as the denoising, unwrapping, the local sensitivity vector estimation and the local shearing angle estimation needed to get quantitative gradient-maps. To validate the technique and its calibration, results obtained from shearography are compared to results obtained from scanning laser vibrometry. Beams are acoustically excited to vibrate at their first resonant frequency and the mode shape is recorded using both shearography and scanning laser vibrometry. Outputs are compared and their properties discussed. Separate inverse method algorithms are developed to process the data for each method. They use the recorded mode shape information to identify the beam’s local stiffness distribution. The beam’s stiffness is also estimated analytically from the local geometry. The local stiffness distributions computed using these methods are compared and the results discussed.
Increasing oil prices have intensified the trend to use composite materials in so-call primary co... more Increasing oil prices have intensified the trend to use composite materials in so-call primary components of cars and in aerospace applications. As a consequence, the fatigus behaviour of composites has became an important issue. This paper describeds accelerated fatigue tests on composite material beam specimens clamped in their middle part and fixed on an electromechanic shaker. Many loading cycles can be imposed on a specimen in a controlled way by inducing resonance vibrations. The bending mode shape that is associated to the fundamental resonance frequency causes a stress state in the specimen that is maximal at the clamping pont in the middle and zero at both free ends. The stress state and hence the fatigue behavior varies from point to point. By interrupting the fatigue test at well-chosen moments in time and measuring the amplitude distribution of the vibration mode, it is possible to calculate the evolutio of the beam stiffness as a function of the number of applied loadin...
The mixed numerical/experimental techniques (MNET), in which the numerical results are correlated... more The mixed numerical/experimental techniques (MNET), in which the numerical results are correlated with experimental data in an iterative fashion, has been developing for more than two decades. An overview of the various estimation algorithms in the MNET is given. Emphasis is placed on the different philosophies which may lead to a deterministic optimisation procedure, or a statistical estimator, or a combination of the two. Formulations, limitations and internal relations of the algorithms are also presented. All the discussions are oriented to the researchers and engineers who are interested in the design optimisation, parameter identification and finite element model updating.
The basic principle of an inverse modeling procedure as it is used for parameter identification, ... more The basic principle of an inverse modeling procedure as it is used for parameter identification, is the generation of a complex and heterogeneous deformation field that contains as much information as possible about the parameters to be identified. One way of obtaining such a non-homogeneous deformation is by making the geometry of the specimen less regular. Another possibility is to make the loading conditions more complex. In this paper both options are actually combined by using a biaxial tensile test on a cruciform specimen in order to identify the parameters of a Swift isotropic hardening law. The yield criterion is modeled by the isotropic Von Mises criterion. The optimization technique used is a constrained gradient based Newton-type routine, which means that in every iteration step, a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be optimized. The functional to be minimized is a least-squares expression of the d...
Incremental forming is a generalized term of metal forming processes where tools of common shapes... more Incremental forming is a generalized term of metal forming processes where tools of common shapes are used to form a small portion of the work piece consecutively next to another resulting in a desired shape. Where die-sets are exclusively designed for particular shapes, one can produce complex forms using a combination of a simple tool and a simplified die. [1,2,5,6] Although ordinary press forming requires less time and is more cost effective in large series production than incremental forming, this new process offers interesting perspectives in small volume production and rapid prototyping [1,2,5,6]
The accuracy of a Finite Element Simulation for plastic deformation strongly depends on the chose... more The accuracy of a Finite Element Simulation for plastic deformation strongly depends on the chosen constitutive laws and the value of the material parameters within these laws. The identification of those mechanical parameters can be done based on homogeneous stress and strain fields such as those obtained in uniaxial tensile tests and simple shear tests performed in different plane material directions. Another way to identify plastic material parameters is by inverse modeling of an experiment exhibiting a heterogeneous stress and strain field. Experimental forces and strains are in this case compared to the simulated ones and it is tried to reduce the difference in a least-squares sense by optimizing the model parameters. The optimization technique used is this case is gradient based, which means that at every iteration a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be identified. The basic principle of the inverse mo...
The quest for more sophisticated methods imparts a significant challenge in the field of nondestr... more The quest for more sophisticated methods imparts a significant challenge in the field of nondestructive testing (NDT) and material characterization. In this paper, we present and discuss experimental polar scans of typical carbon fibre reinforced composite materials recorded with shock wave transducers at frequencies ranging from 1 to 5 MHz. Besides the well-known measurements performed in transmission (T) and double through transmission (2T), we here introduce new investigations based on polar scans of both the backscattered and the double-double through transmission (4T) signals. Amplitude as well as the time of flight diffraction (TOFD) values of the peak amplitude are recorded as a function of the scanned solid angle. One the one hand, it is shown that sharper and more detailed polar scans, especially in TOFD recording, are obtained with the 4T method, which is advantageous for stable polar contour extraction and consequently for inferring the elasticity constants C-ij of the ma...
Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained partic... more Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained particular interest in rapid prototyping and small volume production. The study of the underlying forming mechanisms is supported by new developments in finite element simulations and experimental full field strain measurements. This article aims to describe the possibilities and difficulties encountered during validation of finite element predictions of the incremental forming process. The drawing of a straight line into a metal plate was selected as a first test case for this kind of validation. Results of both finite element simulation and experimental work will be discussed.
Since there is a large demand for biaxial experimental data to evaluate existing failure criteria... more Since there is a large demand for biaxial experimental data to evaluate existing failure criteria, a plane biaxial test device was developed at the Vrije Universiteit Brussel. In-plane loads are applied to a cruciform specimen in order to create a known biaxial stress state in the centre of the specimen. The experiments accomplished in the past and present at the author’s institution have as main intention the biaxial strength and stiffness characterization of fibre-reinforced composite materials. The results from quasi-static tests have been analysed thoroughly in the past [1,2]. The study of the biaxial fatigue behaviour is however in a less advanced stage.